Use of graft polymers

ABSTRACT

The invention relates to the use of graft polymers obtained by polymerization in two stages. In a first stage, at least one graft basis is produced by radically polymerizing a monomer composition A) containing 0 to 40 percent by weight of one or several ethylenically unsaturated ester compounds of formula (I), wherein R represents hydrogen or methyl, R 1  represents a linear or branched alkyl radical comprising 1 to 5 carbon atoms, R 2  and R 3  independently represent hydrogen or a group of formula —COOR′, wherein R′ represents hydrogen or an alkyl group comprising 1 to 5 carbon atoms, 60 to 100 percent by weight of one or several ethylenically unsaturated ester compounds of formula (II), wherein R represents hydrogen or methyl, R 4  represents a linear or branched alkyl radical comprising 6 to 40 carbon atoms, R 5  and R 6  independently represent hydrogen or a group of formula —COOR′, wherein R′ represents hydrogen or an alkyl group comprising 6 to 40 carbon atoms, and 0 to 40 percent by weight of comonomers, the percentages being relative to the weight of monomer composition A). In a second stage, a monomer composition B) containing 20 to 100 percent by weight of at least one monomer that comprises at least one nitrogen-containing group is grafted onto the graft basis in order to reduce wear in lubricant oil compositions. Said graft polymer comprises a maximum of 200 ppm of sulfur while the weight ratio between monomer composition A) and monomer composition B) ranges between 99.7:0.3 and 80:20.

The present invention relates to the use of graft copolymers.

According to the present state of the art, crankshaft drive, pistongroup, cylinder bore and the valve control system of an internalcombustion engine are lubricated with a motor oil. This is done bydelivering the motor oil which collects in the oil sump of the engine bymeans of a delivery pump via an oil filter to the individual lubricationsites (pressure circulation lubrication in conjunction with injectionand oil-mist lubrication).

In this system, the motor oil has the functions of: transmitting forces,reducing friction, reducing wear, cooling the components and gas sealingof the piston.

The oil is supplied under pressure to the bearing points (crankshaft,piston rod and camshaft bearings). The lubrication sites of the valvedrive, the piston group gears and chains are supplied with injected oil,spin-off oil or oil mist.

At the individual lubrication sites, forces to be transmitted, contactgeometry, lubrication rate and temperature vary within wide ranges inoperation.

The increase in the power density of the engines (kW/capacity andtorque/capacity) leads to higher component temperatures and surfacepressures of the lubrication sites.

To ensure the motor oil functions under these operating conditions, theengine manufacturers require proof of the performance of a motor oil inthe form of test results of standardized test methods and engine tests(for example API classification in the USA or ACEA test sequences inEurope). In addition test methods self-defined by individualmanufacturers are used before a motor oil is approved for use.

Testing in passenger vehicle and truck engines customary on the marketensures that wear phenomena caused by motor oil are recognized beforeapproval is granted.

Among the abovementioned lubricant oil properties, the wear protectionof the motor oil is of particular significance. As an example, therequirement list of the ACEA test sequences 2002 shows that, in eachcategory (A for passenger vehicle gasoline engines, B for passengervehicle diesel engines and E for truck engines) with a separate enginetest, sufficient wear protection for the valve drive is to be confirmed.

As mentioned above the approval processes of individual manufacturersinclude additional further engine tests with their own engines and testprograms for assessing the wear performance.

Wear-reducing additives are known from the prior art. However, suchadditives are expensive and some of them have compatibility problems.Such additives are usually phosphorus- and/or sulfur-containing. In thiscontext, it should be taken into account that there is a drive withinthe lubricant industry to reduce the phosphorus and sulfur input inmodern lubricant oil formulations. This has both technical (avoidance ofexhaust gas catalytic converter poisoning) and environmental policyreasons. The search for phosphorus and sulfur-free lubricant additiveshas thus become, specifically in the recent past, an intensive researchactivity of many additive manufacturers.

The article “The contribution of new dispersant mixed polymers to theeconomy of engine oils” (Pennewiss, Auschra) published in LubricationScience (1996, 8, 179-197) discusses the advantageous effects ofadditives composed of ethylene-propylene copolymers and methacrylates,which contain partly ethoxylated side chains. Effects of this chemistryon dispersant action in motor oils are indicated. Advantages in the wearbehavior are likewise described. The systems used have to be prepared inrelatively complicated dispersion processes.

NL 6505344 (Oct. 20, 1966) of Shell describes a synergistic mode ofaction of oil-soluble polymers with typical wear-reducing additivetypes, for example dispersed calcium salts or hydroxides.

U.S. Pat. No. 3,153,640 (Oct. 20, 1964) of Shell includes copolymersconsisting of two parts of methacrylate monomers and one part of NVP.They are not graft copolymers. The advantageous influence on wear inlubricant applications is mentioned. However, the improvement isrelatively limited. This is the case especially taking account of thehigh content of expensive comonomers, for example N-vinylpyrrolidone(NVP).

JP 05271331 (Nippon Oil) describes VI and wear-improving polymersprepared from copolymers of α-olefins and maleic acid which aresubsequently functionalized. The abstract cites friction and wearresults which have been obtained in the Falex test (block-on-ring).

E. H. Okrent states in ASLE Transactions (1961, 4, 97-108), thatpolyisobutylenes or PAMA polymers used as VI improvers having influenceon the wear performance in the engine. No conclusions are made about thechemistry used and the specific composition of the polymers.Wear-reducing action is accounted for merely with viscoelastic effectsof polymer-containing oils. For example, no differences were found ininfluence on wear between PAMA- and PIB-containing oils.

Literature publications by Neudörfl and Schödel (Schmierungstechnik1976, 7, 240-243; SAE Paper 760269; SAE Paper 700054; Die AngewandteMakromolekulare Chemie 1970, 2, 175-188) emphasize in particular the ofthe polymer concentration the engine wear. Reference is made to theabovementioned article by E. H. Okrent and, in analogy to Okrent, awear-reducing action is not connected with the chemistry of the polymer.Generally, it is concluded that viscosity index improvers of relativelylow molecular weight bring improved wear results. One publicationadditionally also discusses wear as a function of the HT/HS properties.

Like Neudörfl and Schödel, K. Yoshida (Tribology Transactions 1990, 33,229-237) ascribes merely viscometric aspects to effects of polymers onthe wear performance, Advantageous effects are explained by thepreferential tendency to elastohydrodynamic film formation.

EP 164807 (Dec. 18, 1985) of Agip describes a multifunctional VIimprover with dispersant, detergent and low-temperature action.Additionally mentioned, but not in the focus of this invention, is awear-reducing action which is attributed, if anything, to advantages inthe corrosion behavior, i.e. to an indirect influence on wear. Thecomposition comprises the VI improver which comprises specificsulfur-containing units. The wear-reducing action of sulfur compounds isknown. However, the use of sulfur compounds is associated withdisadvantages, so that there are efforts to avoid the use of suchcompounds (cf. Lubricants and Lubrication, Wiley-VCH 2001, T. Mang andW. Dresel, p. 191).

In view of the prior art, it is thus an object of the present inventionto provide highly active wear-reducing additives which have a lowcontent of undesired substances, for example phosphorus and/or sulfur,the same time, the additives should overall have high environmental orcompatibility.

In addition, it is consequently an object of the present invention toprovide additives with wear-reducing action which can be preparedparticularly inexpensively.

Furthermore, it is an object of the present invention to provideadditives which stability against oxidation and thermal stress and alsohigh shear resistance. Furthermore, the additives should be soluble inlarge amounts even in very nonpolar lubricant oils, for example in fullysynthetic oils.

In addition it is an object of the present invention to provideadditives which, in addition to wear-reducing action, additionallyimprove the flow properties of the lubricant oils, i.e. have viscosityindex-improving action.

These and also further objects which are not stated explicitly but whichcan be derived or discerned from the connections discussed herein by wayof introduction are achieved by a use with all features of claim 1.Appropriate modifications of the inventive use are protected in theclaims referring back to claim 1.

By using graft copolymers obtainable by a two-stage polymerization, atleast one graft base being prepared in a first stage by free-radicallypolymerizing a monomer composition A) which contains from 0 to 40% byweight, based on the weight of the monomer composition A), of one ormore ethylenically unsaturated ester compounds of the formula (I)

where R is hydrogen or methyl, R¹ is a linear or branched alkyl radicalhaving from 1 to 5 carbon atoms, R² and R³ are each independentlyhydrogen or a group of the formula —COOR′ where R′ is hydrogen or analkyl group having from 1 to 5 carbon atoms, from 60 to 100% by weight,based on the weight of the monomer composition A), of one or moreethylenically unsaturated ester compounds of the formula (II)

where R is hydrogen or methyl, R⁴ is a linear or branched alkyl radicalhaving from 6 to 40 car bon atoms, R⁵ and R⁶ are each independentlyhydrogen or a group of the formula —COOR″ where R″ is hydrogen or analkyl group having from 6 to 40 carbon atoms, andfrom 0 to 40% by weight, based on the weight of the monomer compositionA), of comonomers, anda monomer composition B) which includes from 20 to 100% by weight of atleast one monomer having at least one nitrogen-containing group beinggrafted in a second stage onto the graft base,in whichthe graft copolymer comprises at most 200 ppm of sulfur and the ratio ofthe weight of the monomer composition A) to the weight of the monomercomposition B) is in the range from 99.7:0.3 to 80:20, for reducing wearin lubricant oil compositions, additives are provided which can beprepared particularly inexpensively.

At the same time, a series of further advantages can be achieved by theinventive lubricant composition. These include: the additives to be usedin accordance with the present invention exhibit high stability againstoxidation and thermal stress and high shear resistance.

The inventive use provides additives for wear reduction which aresoluble in large amounts in very nonpolar lubricant oils, for example infully synthetic oils. At the same time, the additives exhibit highcompatibility with lubricant oils.

As a consequence of the inventive use, additives are provided which, inaddition to wear-reducing action, additionally improve the flowproperties of the lubricant oils, i.e. have viscosity index-improvingaction.

In addition, the inventive use of the additive in many cases reduces theenergy consumption.

Graft copolymers which are used for wear reduction in accordance withthe invention may be obtained by a polymerization which comprises atleast two steps.

In a first step, at least one graft base can typically be obtained, ontowhich a graft is grafted in at least one second step.

In the context of the present invention, the term graft base refers toat least one polymer onto which side chain polymers can be grafted. Thegraft base is in many cases also referred to as main chain polymer,backbone polymer or graft substrate.

In a first step a mono mer composition A) which comprises from 0 to 40%by weight, preferably from 0.1 to 35 and more preferably from 1 to 20%by weight, based on the weight of the monomer composition A), of one ormore ethylenically unsaturated ester compounds of the formula (I)

where R is hydrogen or methyl, R¹ is a linear or branched alkyl radicalhaving from 1 to 5 carbon atoms, R² and R³ are each independentlyhydrogen or a group of the formula —COOR′ where R′ is hydrogen or analkyl group having from 1 to 5 carbon atoms from 60 to 100% by weight,preferably from 65 to 99.9 and more preferably from 80 to 99% by weight,based on the weight of the monomer composition A), of one or moreethylenically unsaturated ester compounds of the formula (II)

where R is hydrogen or ethyl, R⁴ is a linear or branched alkyl radicalhaving from 6 to 40 carbon atoms, R⁵ and R⁶ are each independentlyhydrogen or a group of the formula —COOR″ where R″ is hydrogen or analkyl group having from 6 to 40 carbon atoms, and from 0 to 40% byweight, based on the weight of the monomer composition A), of comonomersmay be free-radically polymerized.

Monomer compositions for preparing the graft base comprise one or moreethylenically unsaturated ester compounds of the formula (I)

where R is hydrogen or methyl, R¹ is a linear or branched alkyl radicalhaving from 1 to 5 carbon atoms, R² and R³ are each independentlyhydrogen or a group of the formula —COOR′ where R′ is hydrogen or analkyl group having from 1 to 5 carbon atoms.

Examples of component a) include

(meth)acrylates, fumarates and maleates which derive from saturatedalcohols, such as methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate isopropyl(meth)acrylate, n-butyl(meth)acrylate,tert-butyl (meth)acrylate and pentyl(meth)acrylate;

cycloalkyl(meth)acrylates such as cyclopentyl(meth)acrylate;

-   (meth)acrylates which derive from unsaturated alcohols, such as    2-propynyl(meth)acrylate, allyl(meth)acrylate and    vinyl(meth)acrylate.

When the expression (meth)acrylates is used in the context of thepresent application, this term in each case encompasses methacrylates oracrylates alone, or else mixtures of the two.

As a further constituent, the compositions to be polymerized to preparepreferred graft bases contain from 60 to 100% by weight, in particularfrom 65 to 98% by weight and more preferably from 70 to 90% by weight,based on the weight of the monomer compositions for preparing the graftbase, of one or more ethylenically unsaturated ester compounds of theformula (II)

where R is hydrogen or methyl, R⁴ is a linear or branched alkyl radicalhaving from 6 to 40 carbon atoms, p5 and R⁶ are each independentlyhydrogen or a group of the formula —COOR″ where R″ is hydrogen or analkyl group having from 6 to 40 carbon atoms.

These include

(meth)acrylates, fumarates and maleates which derive from saturatedalcohols, such as hexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,heptyl (meth)acrylate, 2-tert-butylheptyl(meth)acrylate,octyl(meth)acrylate, 3-isopropylheptyl(meth)acrylate,nonyl(meth)acrylate, decyl (meth)acrylate, undecyl(meth)acrylate,5-methylundecyl(meth)acrylate, dodecyl(meth)acrylate,2-methyldodecyl(meth)acrylate, tridecyl(meth)-acrylate,5-methyltridecyl(meth)acrylate, tetradecyl(meth)acrylate,pentadecyl(meth)acrylate, hexadecyl(meth)acrylate, 2-methylhexadecyl(meth)acrylate, heptadecyl(meth)acrylate, 5-isopropylheptadecyl(meth)acrylate, 4-tert-butyloctadecyl(meth)acrylate, 5-ethyloctadecyl(meth)acrylate, 3-isopropyloctadecyl(meth acrylate, octadecyl(meth)acrylate, nonadecyl(meth)acrylate, eicosyl(meth)acrylate,cetyleicosyl(meth)acrylate, stearyleicosyl(meth)acrylate, docosyl(meth)acrylate and/or eicosyltetratriacontyl(meth)acrylate;cycloalkyl(meth)acrylates such as 2,4,5-tri-t-butyl-3-vinylcyclohexyl(meth)acrylate, 2,3,4,5-tetra-t-butylcyclohexyl(meth)acrylate;(meth)acrylates which derive from unsaturated alcohols, for exampleoleyl (meth)acrylate;

cycloalkyl(meth)acrylates such as 3-vinylcyclohexyl(meth)acrylate,cyclohexyl(meth)acrylate, bornyl(meth)acrylate; and the correspondingfumarates and maleates.

The ester compounds having a long-chain alcohol radical, especially thecompounds according to component (b), can be obtained, for example, byreacting (meth)acrylates, fumarates, maleates and/or the correspondingacids with long-chain fatty alcohols, which generally gives a mixture ofesters, for example (meth)acrylates with various long-chain alcoholradicals. These fatty alcohols include Oxo Alcohol® 7911 and OxoAlcohol® 7900, Oxo Alcohol® 1100 Alfol® 61, Alfol® 810, Lial® 125 andNafol® types (Sasol Olefins & Surfactants GmbH); Alphanol® 79 (ICI)Epal® 610 and Epal® 810 (Ethyl Corporation); Linevol® 79, Linevol® 911and Neodol® 25E (Shell A); Dehydad®, Hydrenol® and Lorol® types(Cognis); Acropol® 35 and Exxal® 10 (Exxon Chemicals GmbH); Kalcol 2465Kao Chemicals).

Among the ethylenically unsaturated ester compounds, particularpreference is given to the (meth)acrylates over the maleates andfumarates, i.e. R², R³, R⁵ and R⁶ of the formulae (I) and (II) are eachhydrogen in particularly preferred embodiments. In general, preferenceis given to the methacrylates over the acrylates.

In a particular aspect of the present invention, preference is given tousing mixtures of long-chain alkyl(methacrylates according to thecomponent of the formula (II), the mixtures comprising at least one(methacrylate having from 6 to 15 carbon atoms in the alcohol radicaland at least one (meth)acrylate having from 16 to 40 carbon atoms in thealcohol radical.

The content of the (meth)acrylates having from 6 to 15 carbon atoms inthe alcohol radical is preferably in the range from 20 to 95% by weight,based on the weight of the monomer composition for preparing the graftbase. The content of the (meth)acrylates having from 16 to 40 carbonatoms in the alcohol radical is preferably in the range from 0.5 to 60%by weight based on the weight of the monomer composition for preparingthe graft base.

In a further aspect of the present invention the content of olefinicallyunsaturated esters having from 8 to 14 carbon atoms is preferablygreater than or equal to the content of olefinically unsaturated estershaving from 16 to 18 carbon atoms.

Preferred mixtures for preparing preferred graft bases may additionallyin particular comprise ethylenically unsaturated comonomers which can becopolymerized with the ethylenically unsaturated ester compounds of theformulae (I) and/or (II). The content of comonomers is preferably in therange from 0 to 40% by weight, in particular from 2 to 35% by weight andmore preferably from 5 to 30% by weight based on the weight of themonomer compositions for preparing the graft base.

Comonomers which are particularly suitable in this context for thepolymerization according to the present invention correspond to theformula:

in which R¹* and R²* are each independently selected from the groupconsisting of hydrogen halogens, CN, linear or branched alkyl groupshaving from 1 to 20, preferably from 1 to 6 and more preferably from 1to 4, carbon atoms which may be substituted by from 1 to (2n+1) halogenatoms, where n is the number of carbon atoms of the alkyl group (forexample CF₃), α,β-unsaturated linear or branched alkenyl or alkynylgroups having from 2 to 10, preferably from 2 to 6 and more preferablyfrom 2 to 4, carbon atoms which may be substituted by from 1 to (2n−1)halogen atoms, preferably chlorine, where n is the number of carbonatoms of the alkyl group, for example CH₂═CCl−, cycloalkyl groups havingfrom 3 to 8 carbon atoms which may be substituted by from 1 to (2n−1)halogen atoms, preferably chlorine, where n is the number of carbonatoms of the cycloalkyl group; aryl groups having from 6 to 24 carbonatoms which may be substituted by from 1 to (2n−1) halogen atoms,preferably chlorine, and/or alkyl groups having from 1 to 6 carbonatoms, where n is the number of carbon atoms of the aryl group; C(═Y)R⁵,C(═Y*)NR⁶*R⁷*, Y*C(═Y*)R⁵*, SOR⁵*, SO₂R⁵*, SO₂k⁵*NR⁸SO₂R⁵, PR⁵*₂,P(═Y*)R⁵*₂, Y*PR⁵*₂, P(═Y*)R⁵*₂, NR⁸*₂ which may be quaternized with anadditional R⁸*, aryl or heterocyclyl group, where Y may be NR⁸*, S or O,preferably O; R⁵* is an alkyl group having from 1 to 20 carbon atoms, analkylthio having from 1 to 20 carbon atoms, OR¹⁵ (R¹⁵ is hydrogen or analkali metal), alkoxy of from 1 to 20 carbon atoms, aryloxy orhetero-cyclyloxy; R⁶* and R⁷* are each independently hydrogen or analkyl group having from 1 to 20 carbon atoms, or R⁶* and R⁷* togethermay form an alkylene group having from 2 to 7, preferably from 2 to 5carbon atoms, in which case they form a 3- to 8-membered, preferably 3-to 6-membered, ring, and R⁸ is hydrogen, linear or branched alkyl oraryl groups having from 1 to 20 carbon atoms;R³* and R⁴* are independently selected from the group consisting ofhydrogen, halogen (preferably fluorine or chlorine), alkyl groups havingfrom 1 to 6 carbon atoms and COOR⁹* in which R⁹* is hydrogen, an alkalimetal or an alkyl group having from 1 to 40 carbon atoms, or R³* and R⁴*together may form a group of the formula (CH₂)_(n), which may besubstituted by from 1 to 2n′ halogen atoms or C₁ to C₄ alkyl groups, orform the formula C(═O)—Y*—C(═O) where n′ is from 2 to 6, preferably 3 or4, and Y* is as defined above; and where at least 2 of the R¹*, R²*, R³*and R₄* radicals are hydrogen or halogen.

Preferred comonomers which may be present in the monomer compositions A)include nitrogen bearing monomers, in which case these correspond tothose present in the monomer composition B).

The preferred comonomers include vinyl halides, for example vinylchloride vinyl fluoride vinylidene chloride and vinylidene fluoride;

vinyl esters such as vinyl acetate;

styrene substituted styrenes having an alkyl substituent in the sidechain for example α-methylstyrene and α-ethylstyrene, substitutedstyrenes having an alkyl substituent on the ring such as vinyltolueneand p-methylstyrene halogenated styrenes, for example monochlorostyrenesdichlorostyrenes, tribromostyrenes and tetrabromostyrenes;

heterocyclic vinyl compounds such as 2-vinyl pyridine 3-vinylpyridine2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine,2,3-dimethyl-5-vinylpyridine vinylpyrimidine, vinylpiperidine,9-vinylcarbazole 3-vinyl-carbazole 4-vinylcarbazole, 1-vinylimidazol,2-methyl-1-vinylimidazole N-vinyl pyrrolidone 2-vinylpyrrolidone,N-vinylpyrrolidine, 3-vinylpyrrolidine N-vinylcaprolactam,N-vinylbutyrolactam, vinyloxolane, vinylfuran, vinyloxazoles andhydrogenated vinyloxazoles,

vinyl and isoprenyl ethers;

maleic acid and maleic acid derivatives, for example maleic anhydride,methylmaleic anhydride, maleimide, methylmaleimide;

fumaric acid and fumaric acid derivatives;

acrylic acid and methacrylic acid;

dienes, for example divinylbenzene;

aryl(meth)acrylates such as benzyl, methacrylate or phenyl methacrylate,where the aryl radicals may each be unsubstituted or up totetrasubstituted;

methacrylates of halogenated alcohols, such as

-   2,3-dibromopropyl methacylate,-   4-bromophenyl methacrylate,-   1,3-dichloro-2-propyl methacrylate,-   2-bromoethyl, ethacrylate.-   2-iodoethyl methacrylate,-   chloromethyl methacrylate;    hydroxyalkyl(meth)acrylates such as-   3-hydroxypropyl methacrylate,-   3,4-dihydroxybutyl methacrylate,-   2-hydroxyethyl methacrylate,-   2-hydroxypropyl methacrylate,-   2,5-dimethyl-1,6-hexanediol (meth)acrylate,-   1,10-decanediol (meth)acrylate,    carbonyl-containing methacrylates such as-   2-carboxyethyl methacrylate,-   carboxymethyl methacrylate,-   oxazolidinylethyl methacrylate,-   N-(methacryloyloxy)formamide,-   acetonyl methacrylate,-   N-methacryloylmorpholine,-   N-methacryloyl-2-pyrrolidinone,-   N-(2-methacryloyloxyethyl)-2-pyrrolidinone,-   N-(3-methacryloyloxypropyl)-2-pyrrolidinone,-   N-(2-methacryloyloxypentadecyl)-2-pyrrolidinone,-   N-(3-methacryloyloxyheptadecyl)-2-pyrrolidinone;    glycol dimethacrylates such as 1,4-butanediol methacrylate,    2-butoxyethyl methacrylate, 2-ethoxyethoxymethyl methacrylate,-   2-ethoxyethyl methacrylate;    methacrylates of ether alcohols, such as-   tetrahydrofurfuryl methacrylate;-   vinyloxyethoxyethyl methacrylate,-   methoxyethoxyethyl methacrylate,-   1-butoxypropyl methacrylate,-   1-methyl-(2-vinyloxy)ethyl methacrylate,-   cyclohexyloxymethyl methacrylate,-   methoxymethoxyethyl methacrylate,-   benzyloxymethyl methacrylate,-   furfuryl methacrylate,-   2-butoxyethyl methacrylate,-   2-ethoxyethoxymethyl methacrylate,-   2-ethoxyethyl methacrylate,-   allyloxymethyl methacrylate,-   1-ethoxybutyl methacrylate, methoxymethyl methacrylate,-   1-ethoxyethyl methacrylate,    ethoxymethyl methacrylate and ethoxylated (meth)acrylates which have    preferably from 1 to 20, in particular from 2 to 8, ethoxy groups;    aminoalkyl(meth)acrylates and aminoalkyl(meth)acrylatamides, such as-   N-(3-dimethylaminopropyl)methacrylamide,-   dimethylaminopropyl methacrylate,-   3-diethylaminopentyl methacrylate,-   3-dibutylaminohexadecyl(meth)acrylate;    nitriles of (meth)acrylic acid and other nitrogen-containing    methacrylates, such as-   N-(methacryloyloxyethyl)diisobutyl ketimine,-   N-(methacryloyloxyethyl)dihexadecyl ketimine,-   methacryloylamidoacetonitrile,-   2-methacryloyloxyethylmethylcyanamide,-   cyanomethyl methacrylate;    heterocyclic (meth)acrylates such as-   2-(1-imidazolyl)ethyl(meth)acrylate,    2-(4-morpholinyl)ethyl(meth)acrylate and    1-(2-methacryloyloxyethyl)-2-pyrrolidone;    oxiranyl methacrylates such as-   2,3-epoxybutyl methacrylate,-   3,4-epoxybutyl methacrylate,-   10,11-epoxyundecyl methacrylate,-   2,3-epoxycyclohexyl methacrylate,-   10,11-epoxyhexadecyl methacrylate;-   glycidyl methacrylate.

These monomers may be used individually or as a mixture.

The graft base preferably has a specific viscosity η_(sp/c) measured inchloroform at 25° C. in the range from 4 to 60 ml/g, more preferably inthe range from 5 to 40 ml/g, measured to ISO 1628-6.

The weight-average molecular weight of the graft base is generally lessthan or equal to 600 000 g/mol preferably less than or equal to 400 000g/mol. The weight-average molecular weight of the graft base ispreferably in the range from 5000 to 200 000 g/mol, in particular from6000 to 100 000 g/mol.

The preferred graft bases which can be obtained by polymerizingunsaturated ester compounds preferably have a polydispersity M_(w)/M_(n)in the range from 1.1 to 10.0, in particular from 1.2 to 7.0 and morepreferably from 1.3 to 5.0.

The molecular weight and the polydispersity can be determined by knownmethods. For example, gel permeation chromatography (GPC) can be used.It is equally possible to use an osmometric process for example vaporphase osmometry, to determine the molecular weights. The processesmentioned are, for example, described in P. J. Flory, “Principles ofPolymer Chemistry” Cornell University Press (1953), Chapter VII, 266-316and “Macromolecules, an introduction to Polymer Science”, F. A. Boveyand F. H. Winslow, Editors, Academic Press (1979), 296-312 and W. W.Yau, J. J. Kirkland and D. D. Bly, “Modern Size Exclusion LiquidChromatography, John Wiley and Sons, New York, 1979. To determine themolecular weights of the polymers presented herein, preference is givento using gel permeation chromatography. Measurement should preferably bemade against polymethyl acrylate or polyacrylate standards.

Customary free-radical polymerization is described, inter alia, inUllmann's Encyclopedia of Industrial Chemistry, Sixth Edition. Ingeneral, a polymerization inhibitor and a chain transferee are used forthis purpose. The usable initiators include the azo initiators widelyknown in the technical field, such as AIBN and1,1-azobiscyclohexanecarbonitrile, and also peroxy compounds such asmethyl ethyl ketone peroxide, acetyl-acetone peroxide, dilaurylperoxide, tert-butyl per-2-ethylhexanoate, ketone peroxide, tert-butylperoctoate, methyl isobutyl ketone peroxide, cyclohexanone peroxide,dibenzoyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxyisopropylcarbonate,2,5-bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane, tert-butylperoxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate,dicumyl peroxide, 1,1-bis(tert-butylperoxy)-cyclohexane,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, cumylhydroperoxide, tert-butyl hydroperoxide, bis(4-tert-butylcyclohexyl)peroxydicarbonate, mixtures of two or more of the aforementionedcompounds with one another, and mixtures of the aforementioned compoundswith compounds which have not been mentioned but can likewise form freeradicals.

Suitable chain transferers are in particular sulfur-free compounds whichare known per se. These include, for example, without any intention thatthis should impose a restriction, dimericα-ethylstyrene(2,4-diphenyl-4-methyl-1-pentene), enol ethers ofaliphatic and/or cycloaliphatic aldehydes, terpenes, α-terpinene,terpinols, 1,4-cyclohexadiene, 1,4-dihydronaphthalene,1,4,5,8-tetrahydronaphthalene, 2,5-dihydrofuran, 2,5-dimethylfuranand/or 3,6-dihydro-2H-pyran; preference is given to dimericα-ethylstyrene.

These chain transferers are commercially available. They can also beprepared in the manner known to those skilled in the art. For instance,the preparation of dimeric α-methylstyrene is described in the patent DE966 375. Enol ethers of aliphatic and/or cycloaliphatic aldehydes aredisclosed in the patent DE 3 030 373. The preparation of terpenes isexplained in EP 80 405. The published specifications JP 73/121 891 andJP 78/121 890 explain the preparation of α-terpinene, terpinols,1,4-cyclohexadiene, 1,4-dihydronaphthalene,1,4,5,8-tetrahydronaphthalene. The preparation of 2,5-dihydrofuran,2,5-dimethylfuran and 3,6-dihydro-2H-pyran is explained in the publishedspecification DE 2 502 283.

The polymerization of the graft base can be performed at standardpressure, reduced pressure or elevated pressure. The polymerizationtemperature too is uncritical. In general, however, it is in the rangeof −20°-200° C., preferably 0°-130° C. and more preferably 70°-120° C.

The polymerization can be performed with or without solvent. The term“solvent” is to be understood here in a wide sense.

Preference is given to performing the polymerization in a nonpolarsolvent. These include hydrocarbon solvents, for example aromaticsolvents such as toluene, benzene and xylene, saturated hydrocarbons,for example cyclohexane, heptane, octane, nonane, decane, dodecane,which may also be present in branched form. These solvents may be usedindividually or else as a mixture. Particularly preferred solvents aremineral oils, natural oils and synthetic oils, and mixtures thereof.Among these, mineral oils are most preferred.

The graft base can be prepared in one or more steps, and it is possibleto use different monomer compositions A) which may differ, for example,in the content of comonomers. This allows mixtures of graft bases to begenerated which can be used advantageously in accordance with theinvention.

To prepare graft polymers from the composition obtained in step 1, whichgenerally comprises at least one main chain polymer, at least onemonomer composition B) is grafted.

It is assumed that the grafting forms side chains on the graft base, sothat at east a portion of the graft is bonded covalently to the graftbase.

The grafting can be effected in one or more steps. In this context, itis possible, inter alia, to change the composition of the monomercomposition B). For example, different monomers havingnitrogen-containing groups can be used.

In addition it is also possible in further stages to graft oncompositions which contain only a small content of nitrogen-containingmonomers, if any. Such graftings can be performed before or after thegrafting with monomers which have nitrogen-containing groups.

The performance of graft copolymerizations is common knowledge and isdetailed, for example, in Ullmann's Encyclopedia of IndustrialChemistry, Sixth Edition and Römpp Chemie-Lexikon on CD version 2.0,where reference is made to further literature.

The monomer composition B) comprises at least 20% by weight, preferablyat least 50% by weight, in particular at least 70% by weight and morepreferably from 90% by weight to 100% by weight, based on the weight ofthe monomer composition B), of at least one monomer having at least onenitrogen-containing group.

The ratio of the weight of the monomer composition A) to the weight ofthe monomer composition B) is in the range from 99.7:0.3 to 80:20,preferably in the range from 99.5:0.5 to 88:12, in particular in therange from 99:1 to 91:9 and more preferably in the range from 98:2 to95:5.

In general, 0.3-12% by weight, in particular 1-9% by weight andpreferably 2-5% by weight, based on the weight of the graft base of oneor more monomers having at least one nitrogen-containing group may begrafted onto the graft base.

Monomers having at east one nitrogen-containing group are commonknowledge. The nitrogen-containing groups preferably have dispersingaction. In addition, preferred nitrogen-containing groups which arepresent in the monomers exhibit basic action. The pK_(b) value of thesebases is preferably in the range from 2 to 7, more preferably from 4 to7.

Preferred groups are from primary, secondary or tertiary amines,saturated and/or unsaturated heterocyclic nitrogen compounds, forexample pyridine, pyrimidine, piperidine, carbazole, imidazole,morpholine, pyrrole.

Preferred monomers having at least one nitrogen-containing group arecompounds of the formula (III)

where R⁷, R⁸ and R⁹ may each independently be hydrogen or an alkyl grouphaving from 1 to 5 carbon atoms and R¹⁰ is a group which contains from 1to 100 carbon atoms and has at least one nitrogen atom. At least two ofthe R⁷, R⁸ and R⁹ radicals are preferably hydrogen.

The R¹⁰ radical is a group comprising from 1 to 100, in particular from2 to 50, preferably from 2 to 20 carbon atoms. The expression “groupcontaining from 1 to 100 carbon atoms” indicates radicals of organiccompounds having from 1 to 100 carbon atoms. It includes aromatic andheteroaromatic groups, and alkyl, cycloalkyl, alkoxy, cycloalkoxy,alkenyl, alkanoyl, alkoxycarbonyl groups, and also heteroaliphaticgroups. The groups mentioned may be branched or unbranched. In addition,these groups may have customary substituents. Substituents are, forexample, linear and branched alkyl groups having from 1 to 6 carbonatoms, for example methyl, ethyl, propyl, butyl, pentyl, 2-methylbutylor hexyl; cycloalkyl groups, for example cyclopentyl and cyclohexyl;aromatic groups such as phenyl or naphthyl; amino groups ether groups,ester groups and halides.

According to the invention, aromatic groups denote radicals of mono- orpolycyclic aromatic compounds having preferably from 6 to 20, inparticular from 6 to 12, carbon atoms. Heteroaromatic groups denote arylradicals in which at least one CH group has been replaced by N and/or atleast two adjacent CH groups have been replaced by S, NH or O,heteroaromatic groups having from 3 to 19 carbon atoms.

Aromatic or heteroaromatic groups preferred in accordance with theinvention derive from benzene, naphthalene, biphenyl, diphenyl ether,diphenylmethane, diphenyldimethylmethane, bisphenone, furan, pyrrole,imidazole, isoxazole, pyrazole, 1,3,4-oxadiazole,2,5-diphenyl-1,3,4-oxadiazole, 1,3,4-triazole,2,5-diphenyl-1,3,4-triazole, 1,2,5-triphenyl-1,3,4-triazole,1,2,4-oxadiazole, 1,2,4-triazole, 1,2,3-triazole, 1,2,3,4-tetrazole,benzofuran, indole, benzo[c]furan, isoindole, benzoxazole,benzimidazole, benzisoxazole, benzopyrazole, dibenzofuran, carbazole,pyridine, bipyridine, pyrazine, pyrazole, pyrimidine, pyridazine,1,3,5-triazine, 1,2,4-triazine, 1,2,4,5-triazine, tetrazine, quinoline,isoquinoline, quinoxaline, quinazoline, cinnoline, 1,8-naphthyridine,1,5-naphthyridine, 1,6-naphthyridine, 1,7-naphthyridine, phthalazine,pyridopyrimidine, purine, pteridine or quinolizine, 4H-quinolizine,diphenyl ether, anthracene, benzopyrrole, benzooxathiadiazole,benzooxadiazole, benzopyridine, benzopyrazine, benzopyrazidine,benzopyrimidine, benzotriazine, indolizine, pyridopyridine,imidazopyrimidine, pyrazino-pyrimidine, carbazole, aciridine, phenazine,benzoquinoline, phenoxazine, acridizine, benzopteridine, phenanthrolineand phenanthrene, each of which a also optionally be substituted.

The preferred alkyl groups include the methyl, ethyl, propyl, isopropyl,1-butyl, 2-butyl, 2-methylpropyl, tert-butyl radical, pentyl,2-methylbutyl, 1,1-dimethylpropyl, hexyl, heptyl, octyl,1,1,3,3-tetramethylbutyl, nonyl, 1-decyl, 2-decyl, undecyl, dodecyl,pentadecyl and the eicosyl group.

The preferred cycloalkyl groups include the cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl and the cyclooctyl group, each ofwhich is optionally substituted with branched or unbranched alkylgroups.

The preferred alkenyl groups include the vinyl, allyl,2-methyl-2-propenyl, 2-butenyl, 2-penetenyl, 2-decenyl and the2-eicosenyl group.

The preferred alkynyl groups include the ethynyl, propargyl,2-methyl-2-propynyl, 2-butynyl, 2-pentynyl and the 2-decynyl group.

The preferred alkanoyl groups include the formyl, acetyl, propionyl,2-methylpropionyl, butyryl, valeroyl, pivaloyl, hexanoyl, decanoyl andthe dodecanoyl group.

The preferred alkoxycarbonyl groups include the methoxycarbonyl,ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, tert-butoxycarbonyl,hexyloxycarbonyl, 2-methylhexyloxycarbonyl, decyloxycarbonyl ordodecyloxycarbonyl group.

The preferred alkoxy groups include alkoxy groups whose hydrocarbonradical is one of the aforementioned preferred alkyl groups.

The preferred cycloalkoxy groups include cycloalkoxy groups whosehydrocarbon radical is one of the aforementioned preferred cycloalkylgroups.

The preferred heteroatoms which are present in the R¹⁰ radical includeoxygen and nitrogen.

In a particular aspect of the present invention, the R¹⁰ group may be a—C(O)—X—R¹¹ group where X=oxygen or an amino group of the formula —NH—or —NR¹²— where R¹² is an alkyl radical having from 1 to 40 carbon atomsand R¹¹ is a linear or branched alkyl radical which is substituted by atleast one —NR¹³R¹⁴ group and has from 2 to 20, preferably from 2 to 6carbon atoms, where R¹³ and R¹⁴ are each independently hydrogen, analkyl radical having from 1 to 20, preferably from 1 to 6, or where R¹³and R¹⁴, including the nitrogen atom and optionally a further nitrogenor oxygen atom, form a 5- or 6-membered ring which may optionally besubstituted by C₁-C₆-alkyl.

In a further preferred embodiment, R¹⁰ may be an —NR¹⁵C(═O)R¹⁶ groupwhere R¹⁵ and R¹⁶ together form an alkylene group having from 2 to 6,preferably from 2 to 4 carbon atoms, to form a 4- to 8-membered,preferably 4- to 6-membered, saturated or unsaturated ring, ifappropriate with inclusion of a further nitrogen or oxygen atom, wherethis ring may optionally also be substituted by C₁-C₆-alkyl.

In a third preferred embodiment, R¹⁰ may be a group which is derivedfrom the heteroaromatic or heterocyclic compounds detailed above.Preferred compounds in this context include pyridine, pyrimidine,piperidine, carbazole, imidazole, morpholine, pyrrole.

The ratio of nitrogen atoms to carbon atoms in the R¹⁰ radical of theformula (III) may, in a particular aspect, be in the range from 1:1 to1:20, preferably from 1:2 to 1:10.

The preferred monomers having at least one nitrogen-containing groupinclude

aminoalkyl(meth)acrylates and aminoalkyl(meth)acrylatamides such as

-   N-(3-dimethylaminopropyl)methacrylamide,-   dimethylaminoethyl methacrylate,-   dimethylaminopropyl methacrylate,-   3-diethylaminopentyl methacrylate,-   3-dibutylaminohexadecyl(meth)acrylate;    heterocyclic (meth)acrylates such as    2-(1-imidazolyl)ethyl(meth)acrylate,    N-morpholinoethyl(meth)acrylate, especially 2-(4-morpholinyl)ethyl    (meth)acrylate and 1-(2-methacryloyloxyethyl)-2-pyrrolidone;    heterocyclic vinyl compounds such as 2-vinylpyridine,    3-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine,    2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, vinylpiperidine,    9-vinylcarbazole, 3-vinyl-carbazole, 4-vinylcarbazole,    1-vinylimidazole, 2-methyl-1-vinylimidazole, N-vinylpyrrolidone,    2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine,    N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxazoles and    hydrogenated vinyloxazoles.

These monomers may be used individually or as a mixture.

In addition, the monomer composition B) may comprise comonomers whichcan be copolymerized with the monomers having at least onenitrogen-containing group. These monomers correspond to the monomerswhich were detailed in relation to the monomer composition A). Thesemonomers may be used individually or as a mixture.

For the grafting, a polymerization initiator is generally used, forwhich the initiators mentioned above for the preparation of the graftbase may be used. Particular preference is given to using cumylhydroperoxide, diisobutyl hydroperoxide or tert-butyl perbenzoate.

The present invention provides additives for wear reduction withouttheir having a high sulfur content. Thus, the sulfur content is at most200 ppm, preferably at most 100 ppm and more preferably at most 5 ppm,based on the weight of the graft copolymer. The low content of sulfurcan be achieved in particular by the use of sulfur-free components.

The grafting can be carried out under standard pressure, reducedpressure or elevated pressure. The polymerization temperature too isuncritical. In general, it is, however, in the range of −20-200° C.,preferably 0°-160° C. and more preferably 110-140° C.

In a particular aspect of the present invention, the graftpolymerization can be effected at a temperature which is higher than thetemperature at which the graft base was formed. The temperature of thegrafting is preferably higher by at least 5° C., preferably by at least10° C. and more preferably by at least 20° C. than the temperature atwhich the graft base was formed.

In a particular aspect of the present invention, the graft yield isgreater than or equal to (x*10⁻⁵ mol/g+35)%, more preferably greaterthan or equal to (x*10⁻⁵ mol/g+40)%, where x is the weight-averagemolecular weight of the graft base determined by GPC. At aweight-average molecular weight of 100 000, the graft yield ispreferably greater than or equal to 36% and more preferably greater thanor equal to 41%.

In a particular aspect of the present invention, the graft yield isgreater than or equal to 35%, in particular greater than or equal to 45%and more preferably greater than or equal to 50%.

The graft yield (PA) is defined as PA=(M_(Pf)−M_(PG))/M_(pf)*100% whereM_(PG) is the mass of the graft base and M_(Pf) the mass of the graftcopolymer in one volume unit.

The mass of the graft base (M_(PG)) and the mass of the graft copolymer(M_(Pf)) can be determined by HPLC chromatography (High PerformanceLiquid Chromatography) which is configured as adsorption chromatography.

For elution, the polarity of the solvent is varied. This can be achievedby changing the solvent composition. Preference is given to using aHewlett Packard HP 1090 liquid chromatograph with a CN-functionalizedsilica gel column (Nucleosil CN-25 cm #N1224).

For elution, preference is given to using a solvent gradient. Elutioncan be effected over 15 minutes. In the first minute, pure isooctane isused. In the region from minute 1 to minute 11, the content of isooctaneis reduced from 100% to 0% with constant gradient, while the content oftetrahydrofuran and methanol is increased from 0% to 50% in each case atconstant gradient. In the region from minute 11 to minute 15, thecontent of methanol is increased from 50% to 100% while the content oftetrahydrofuran is reduced from 50% to 0%. The solvent composition usedwith preference for the elution can be taken from FIG. 1. The HPLCanalysis is preferably performed at a flow rate of 1 ml/min at roomtemperature. The HPLC column can be supplied with a maximum loading, butit should be ensured that all of the polymer is bonded to the column. InHPLC, the graft base is generally eluted before the graft copolymer.

The polymers are detected preferably by the ELSD method (EvaporatingLight Scattering Detector), which is known per se and has been describedin the literature cited above. To convert the units measured to massunits a calibration function is required, which should preferably beeffected immediately before or after the measurement in this case, anAlltech 2000 ELSD detector can be used.

As detailed above the graft yield is found from the equationPA=(M _(Pf) −M _(PG))/M _(Pf).

The mass of the graft copolymer (M_(Pf)) is calculated from thedifference of the total mass of the polymer (M_(Total)) and the mass ofthe graft base M_(PG) by the equation M_(Pf)=M_(Total)−M_(PG).

The total mass of the polymer (M_(Total)) can be determined in a knownmanner, for example by weighing the polymer used for the analysis, orfrom the density, the proportion by weight and the volume of the polymersolution used for the analysis.

The mass of the graft base (M_(PG)) is calculated fromM_(PG) = (∫_(t  1)^(t  2)mAU^(*)𝕕t)^(*)f_(response)where ∫_(t  1)^(t  2)mAU^(*)𝕕t

-   -   Peak area of the graft base in milliabsorbance units*        seconds=mAU*s over the time period from t1 to t2, where t1 is        the start and t2 is the end of the elution of graft base.        f_(response): response factor, function in μg/mAU*s which is        required response to convert the peak area to a mass which is        obtained by means of a calibration curve.

The graft copolymer preferably has a specific viscosity η_(sp/c)measured in chloroform at 25° C. in the range from 5 to 70 ml/g, morepreferably in the range from 6 to 50 ml/g, measured to ISO 1628-6.

The ratio of the specific viscosity of the graft copolymer to thespecific viscosity η of the graft base is preferably in the range from1.01:1 to 1.30:1, in particular in the range from 1.10:1 to 1.20:1.

The weight-average molecular weight of the graft copolymer is preferablyless than or equal to 600 000 g/mol, in particular less than or equal to400 000 g/mol. More preferably, the weight-average molecular weight ofthe graft copolymer is in the range from 5100 to 250 000 g/mol, inparticular from 6500 to 120 000 g/mol.

The ratio of the weight-average molecular weight of the graft copolymerto the weight-average molecular weight of the graft base is preferablyin the range from 1.01:1 to 5:1, in particular in the range form 1.5:1to 2:1.

Moreover, the graft copolymer is used in a lubricant oil composition. Alubricant oil composition comprises at least one lubricant oil.

The lubricant oils include in particular mineral oils, synthetic oilsand natural oils.

Mineral oils are known per se and commercially available. They aregenerally obtained from petroleum or crude oil by distillation and/orrefining and optionally further purification and finishing processes,the term mineral oil including in particular the higher-boilingfractions of crude oil or petroleum. In general, the boiling point ofmineral oil is higher than 200° C., preferably higher than 300° C., at5000 Pa. The production by low-temperature carbonization of shale oil,coking of bituminous coal, distillation of brown coal with exclusion ofair, and also hydrogenation of bituminous or brown coal is likewisepossible, Mineral oils are also produced in a smaller proportion fromraw materials of vegetable (for example from jojoba, rapeseed) or animal(for example neatsfoot oil) origin. Accordingly, mineral oils have,depending on their origin, different proportions of aromatic, cyclic,branched and linear hydrocarbons.

In general, a distinction is drawn between paraffin-base, naphthenic andaromatic fractions in crude oils or mineral oils, in which the termparaffin-base fraction represents longer-chain or highly branchedisoalkanes, and naphthenic fraction represents cycloalkanes. Inaddition, mineral oils, depending on their origin and finishing, havedifferent fractions of n-alkanes, isoalkanes having a low degree ofbranching, known as mono-methyl-branched paraffins, and compounds havingheteroatoms, in particular O, N and/or S, to which a degree of polarproperties is attributed. However, the assignment is difficult, sinceindividual alkane molecules may have both long-chain branched groups andcycloalkane radicals, and aromatic parts. For the purposes of thepresent invention, the assignment can be effected to DIN 51 378, forexample, Polar fractions can also be determined to ASTM D 2007.

The fraction of n-alkanes in preferred mineral oils is less than 3% byweight, the fraction of O-, N- and/or S-containing compounds less than6% by weight. The fraction of the aromatics and of themono-methyl-branched paraffins is generally in each case in the rangefrom 0 to 40% by weight. In one interesting aspect, mineral oilcomprises mainly naphthenic and paraffin-base alkanes which havegenerally more than 13, preferably more than 18 and most preferably morethan 20 carbon atoms. The fraction of these compounds is generally ≧60%by weight, preferably 80% by weight, without any intention that thisshould impose a restriction. A preferred mineral oil contains from 0.5to 30% by weight of aromatic fractions, from 15 to 40% by weight ofnaphthenic fractions, from 35 to 80% by weight of paraffin-basefractions, up to 3% by weight of n-alkanes and from 0.05 to 5% by weightof polar compounds, based in each case on the total weight of themineral oil.

An analysis of particularly preferred mineral oils, which was effectedby means of conventional processes such as urea separation and liquidchromatography on silica gel shows, for example, the followingconstituents, the percentages relating to the total weight of theparticular mineral oil used:

n-alkanes having from approx. 18 to 31 carbon atoms:

0.7-1.0%,

slightly branched alkanes having from 18 to 31 carbon atoms

1.0-8.0%,

aromatics having from 14 to 32 carbon atoms”

0.4-10.7%

iso- and cycloalkanes having from 20 to 32 carbon atoms

60.7-82.4%,

polar compounds

0.1-0.8%,

loss:

6.9-19.4%.

Valuable information with regard to the analysis of mineral oils and alist of mineral oils which have a different composition can be found,for example, in Ullmann's Encyclopedia of industrial Chemistry, 5thEdition on CD-ROM, 1997, under “lubricants and related products”.

Synthetic oils include organic esters, for example diesters andpolyesters, polyalkylene glycols, polyethers, synthetic hydrocarbons,especially polyolefins, among which preference is given topolyalphaolefins (PAO), silicone oils and perfluoroalkyl ethers. Theyare usually somewhat more expensive than the mineral oils, but haveadvantages with regard to their performance.

Natural oils are animal or vegetable oils, for example neatsfoot oils orjojoba oils.

These lubricant oils may also be used as mixtures and are in many casescommercially available.

The concentration of the graft copolymer in the lubricant oilcomposition is preferably in the range from 1 to 40% by weight, morepreferably in the range form 2 to 20% by weight, based on the totalweight of the composition.

In addition to the aforementioned components, a lubricant oilcomposition may comprise further additives.

These additives include antioxidants, corrosion inhibitors, antifoams,antiwear components, dyes, color stabilizers, detergents, pour pointdepressants, DI additives, friction modifiers and/or extreme pressureadditives.

The graft copolymer may be used especially for reducing wear in internalcombustion engines, gearboxes, clutches or pumps.

In a particular aspect of the present invention, the present use maylead to a mean cam wear of at most 40 μm, preferably at most 30 μm andmore preferably at most 20 μm at 100 h, measured to CEC-L-51-A-98.

EXAMPLES

Methods and Test Methods Used:

In general, wear is determined in the engine by a component comparisonbefore and after a wear test by measuring the cam shape. For the presentinvention, measurement was effected by test method CEC-L-51-A-98. Thistest method is suitable both for the analysis of the wear performance ina passenger vehicle diesel engine (ACEA category B) and in a truckdiesel engine (ACEA category E).

In this test method, the circumferential profile of each cam isdetermined and compared in 1° steps on a 2- or 3-D measuring machinebefore and after the test. The profile deviation formed in the testcorresponds to the cam wear. To assess the tested motor oil, the wearproperties of the individual cams are averaged and compared with thelimiting value of the appropriate ACEA categories.

In a departure from the CEC test method, the test time was shortenedfrom 200 h to 100 h. After this test, the cam wear was determined. Asearly as after 100 h, clear differences could be detected in the wearbetween the formulations used.

Synthesis of the polymer used for Example 1 (Polymer Composition I)

A 2 liter four-neck flask equipped with saber stirrer (operated at 150revolutions per minute), thermometer and reflux condenser was initiallycharged with 430 g of a 150N oil and 47.8 g of a monomer mixtureconsisting of C12-C18-alkyl methacrylates and methyl methacrylate (MMA)in a weight ratio of 99.0:1.0. The temperature is adjusted to 100° C.Thereafter, 0.71 g of tert-butyl peroctoate is added and, at the sametime, a monomer feed consisting of 522.2 g of a mixture of C12-C18-alkylmethacrylates and methyl methacrylate in a weight ratio of 99.0:1.0 andalso 3.92 g of tert-butyl peroctoate is started. The feed time is 3.5hours and the feed rate is uniform. Two hours after the end of feeding,another 1.14 g of tert-butyl peroctoate are added. The total reactiontime is 8 hours. The mixture is then heated to 130° C. After the 130° C.have been attained, 13.16 g of a 150N oil, 17.45 g of N-vinylpyrrolidoneand 1.46 g of tert-butyl perbenzoate are added. In each case 1 hour, 2hours and 3 hours thereafter, another 0.73 g each time of tert-butylperbenzoate is added. The total reaction time is 8 hours. Thereafter thepolymer solution of a pour point improver which makes up 7 percent byweight of the total solution is added.

-   -   Specific viscosity (20° C. in chloroform): 29 ml/g    -   Kinematic viscosity at 100° C.: 492 mm²/s    -   Thickening action (10% of the above product in a 150N oil):        -   at 100° C.: 10.97 mm²/s        -   at 40° C., 64.3 m²/s    -   Viscosity index: 164    -   Residual C12-18-alkyl methacrylate monomer content: 0.24%    -   Residual MMA monomer content: 22 ppm    -   Residual N-vinylpyrrolidone monomer content: 0.056%        The graft yield was 55%.        Synthesis of the Polymer Used for Comparison 2 (Polymer        Composition II)

A 2 liter four-neck flask equipped with saber stirrer (operated at 150revolutions per minute), thermometer and reflux condenser is initiallycharged with 400 g of a 150 N oil and 44.4 g of a monomer mixtureconsisting of C12-C18-alkyl methacrylates, methyl methacrylate (MMA) andof a methacrylate ester of an iso-C13-alcohol with 20 ethoxylate unitsin a weight ratio of 87.0/0.5/12.5. The temperature is adjusted to 90°C. After the 90° C. have been attained, 1.75 g of tert-butyl peroctoateare added, and, at the same time, a feed of 555.6 g of a mixtureconsisting of C12-C18-alkyl methacrylates, methyl methacrylate and of amethacrylate ester of an iso-C13-alcohol with 20 ethoxylate units in aweight ratio of 87.0/0.5/12.5 and also 2.78 g of tert-butyl peroctoateis started. The feeding time is 3.5 hours. The feed rate is uniform. Twohours after the end of feeding, another 1.20 g of tert-butyl peroctoateare added. The total reaction time is 8 hours. Thereafter, the polymersolution of a pour point improver is added, which is then present to anextent of 5 percent by weight. The solution is then diluted with anethoxylated iso-C₁₃-alcohol which contains 3 ethoxylate units in a ratioof 79/21.

-   -   Specific viscosity (20° C. in chloroform): 45 ml/g    -   Kinematic viscosity at 100° C.: 400 mm²/s    -   Thickening action (10% of the above product in a 150N oil):        -   at 100° C.; 11.56 mm²/s        -   at 40° C., 63.9 mm²/s    -   Viscosity index: 178    -   Residual C12-18-alkyl methacrylate monomer content: 0.59%    -   Residual MMA monomer content: 48 ppm

Comparative Example 1

As comparative example 1, a motor oil formulation of category SAE 5W-30consisting of a commercial base oil and additives, for example OLOA 4594(DI package) and Nexbase 3043 as the oil component were mixed and testedin the CEC-L-51-A-98 test.

Oloa 4549 (oronite) is a typical DI additive for motor oils. In additionto ashless dispersants, the product also comprises components forimproving the wear performance. The latter components in Oloa 4549 arezinc and phosphorus compounds. Zinc and phosphorus compounds can beregarded as the most common additives at the present time for improvingthe wear behavior.

The thickener and VI improver used was an ethylene-propylene copolymer(Paratone 8002). Even though their VI action is restricted,ethylene-propylene copolymers are currently the most common VI improversin passenger vehicle and truck motor oils owing to their outstandingthickening action.

The composition and the test results of the test methods detailed aboveare shown in Table 1.

Example 1

Comparative example 1 was essentially repeated, except that an inventivepolymer composition I was added to the motor oil formulation. In doingso, the thickening action of the polymer composition I was taken intoaccount with a reduced addition of Paratone 8002 in order to retain theviscosity level of the motor oil formulation. The content of Paratone8002 was thus reduced compared to the formulation of comparativeexample 1. This inventive formulation was likewise tested in theCEC-L-51-A-98 test.

The composition and the test results of the test methods detailed aboveare shown in Table 1.

Comparative Example 2

Comparative example 1 was essentially repeated, except that a PAMApolymer of composition 11 was added to the motor oil formulation. Withregard to the molecular weight and their oil-thickening action, there isno difference between polymer composition I and II. To prepare theformulation for comparative example 2, thus, merely the 3% by weight ofthe nitrogen-containing polymer of polymer composition I was exchangedfor 3% by weight of the ethoxylate-containing polymer composition II.Such ethoxylated PAMA types of polymer composition 11 have beendescribed as dispersible VI improvers, just like the polymer compositionI.

The composition and the test results of the test methods detailed aboveare shown in Table 1. TABLE 1 Com- Com- parison 1 Example 1 parison 2Component SAE 5W-30 SAE 5W-30 SAE 5W-30 Paratone 8002, content 11.5 8.58.5 (% by wt.) (Viscosity index improver) OLOA 4594, content 13.2 13.213.2 (% by wt.) (DI package) Nexbase 3043, content 75.3 75.3 75.3 (% bywt.) (Base oil) Polymer composition I, None 3 None content (% by wt.)Polymer composition II, None None 3 content (% by wt.) Kinematicviscosity at 11.38 11.56 11.91 100° C. (mm²/s) Mean cam wear (μm), 47.418.6 39.9 at 100 h

It was found that the nitrogen-containing polymers have outstandingwear-reducing actions which cannot be explained by virtue of thedispersing action and were not to be expected. N-containing polymers arethus clearly delimited from O-based (ethoxylated) representatives inrelation to their advantageous wear protection function.

1-21. (canceled)
 22. A method of using graft copolymers for reducingwear in lubricant oil compositions, said graft copolymers obtainable bya two-stage polymerization, at least one graft base being prepared in afirst stage by free-radically polymerizing a monomer composition A)which contains from 0 to 40% by weight, based on the weight of themonomer composition A), of one or more ethylenically unsaturated estercompounds of formula (I)

where R is hydrogen or methyl, R¹ is a linear or branched alkyl radicalhaving from 1 to 5 carbon atoms, R² and R³ are each independentlyhydrogen or a group of the formula —COOR′ where R′ is hydrogen or analkyl group having from 1 to 5 carbon atoms, from 60 to 100% by weight,based on the weight of the monomer composition A), of one or moreethylenically unsaturated ester compounds of formula (II)

where R is hydrogen or methyl, R⁴ is a linear or branched alkyl radicalhaving from 6 to 40 carbon atoms, R⁵ and R⁶ are each independentlyhydrogen or a group of the formula —COOR″ where R″ is hydrogen or analkyd group having from 6 to 40 carbon atoms, and from 0 to 40% byweight, based on the weight of the monomer composition A), ofcomonomers, and a monomer composition B) being grafted in a second stageonto the graft base which monomer includes from 2 to 100% by weight ofat east or one monomer having at least one nitrogen-containing group,characterized in that the graft copolymer comprises at most 200 ppm ofsulfur and the ratio of the weight of the monomer composition A) to theweight of the monomer composition B) is in the range from 99.7:0.3 to80:20.
 23. The method as claimed in claim 22, characterized in that theraft yield is greater than or equal to (x*10⁻⁵ mol/g+35) % where x isthe weight-average molecular weight of C the graft base determined byGPC.
 24. The method as claimed in claim 22, characterized in that thegraft base has a weight-average molecular weight in the range from 5000to 200 000 g/mol.
 25. The method as claimed in claim 22, characterizedin that the graft base has a specific viscosity η_(sp/c) measured inchloroform, at 25° C. between 4 and 40 ml/g.
 26. The method as claimedin claim 22, characterized in that the graft base has a specificviscosity η_(sp/c) measured in chloroform at 25° C. between 5 and 50ml/g.
 27. The method as claimed in claim 22, characterized in that theratio of the specific viscosity of the graft copolymer to the specificviscosity of the graft base is in the range from 1.01:1 to 1.30:1. 28.The method as claimed in claim 22, characterized in that the graftcopolymer has a weight-average molecular weight in the range from 5100to 250
 000. 29. The method as claimed in claim 22, characterized in thatthe ratio of the weight-average molecular weight of the graft copolymerto the weight-average molecular weight of the graft base is in the rangefrom 1.01:1 to 5:1.
 30. The method as claimed in claim 22, characterizedin that the polymerization temperature in step 2 is greater than thepolymerization temperature in step
 1. 31. The method as claimed in claim22, characterized in that the polymerization temperature in step 1 is inthe range from 70 to 120° C.
 32. The method as claimed in claim 22,characterized in that the polymerization temperature in step 2 is in therange from 110 to 140° C.
 33. The method as claimed in claim 22,characterized in that the monomer having at least onenitrogen-containing group is a compound of formula (III)

where R⁷, R⁸ and R⁹ may each independently be hydrogen or an alkyl grouphaving from 1 to 5 carbon atoms and R¹⁰ is a group which contains from 1to 100 carbon atoms and has at least one nitrogen atom.
 34. The methodas claimed in claim 33, characterized in that at least one monomerhaving at least one nitrogen-containing group is selected from the groupconsisting of aminoalkyl(meth)acrylates and aminoalkyl (meth)acrylamidesuch as N-(3-dimethylaminopropyl)-methacrylamide, dimethylaminoethylmethacrylate, dimethylaminopropyl methacrylate, 3-diethylaminopentylmethacrylate, 3-dibutylaminohexadecyl(meth)acrylate; heterocyclic(meth)acrylates such as 2-(1-imidazolyl)ethyl(meth)acrylate,N-morpholinoethyl(meth)acrylate, especially2-(4-morpholinyl)ethyl(meth)acrylate and1-(2-methacryloyloxy)-2-pyrrolidone; heterocyclic vinyl compounds suchas 2-vinylpyridine, 3-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl4-vinylpyridine, 2,3-dimethyl-5-vinylpyridine, vinylpyrimidine,vinylpiperidine, 9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole,1-vinylimidazole, 2-methyl-1-vinylimidazole, N-vinylpyrrolidone,2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine,N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxazoles and hydrogenatedvinyloxazoles.
 35. The method as claimed in claim 33, characterized inthat from 1 to 9% by weight, based on the weight of the graft base, ofone or more compounds of the formula (III) are grafted onto the graftbase.
 36. The method as claimed in claim 22, characterized in that thegraft copolymer additionally has viscosity index-improving action and/ordispersing action and/or detergent act on and/or pour point-depressingaction.
 37. The method as claimed in claim 22, characterized in that thegraft copolymer leads to reduced energy consumption.
 38. The method asclaimed in claim 22, characterized in that the lubricant mixturecomprises friction modifiers and/or extreme pressure additives which arenot raft copolymers as claimed in claim
 22. 39. The method as claimed inclaim 22, characterized in that the lubricant oil composition contains2-20 percent by weight of the graft copolymer.
 40. The method as claimedin claim 22, characterized in that the monomer composition A) comprisesnitrogen-bearing monomers.
 41. The method as claimed in claim 22,characterized in that the use leads to a mean cam wear of at most 40 μmafter 100 h measured to CEC-L-51-A-98.
 42. The method as claimed inclaim 22, characterized in that the lubricant oil composition is used tolubricate internal combustion engines, gearboxes) clutches or pumps.